advertising: Parse intervals and tx power from adv

advertising: Parse intervals and tx power from adv

This change adds parsers for the advertising intervals and tx power
properties of the LEAdvertisement1 object. It validates that each field
adheres to the 5.2 spec, and that min and max intervals are compatible
with each other, i.e. that min interval is less than max interval.

A note here for maintainers: The tx power that is sent in the hci
parameter command is an int8_t, but as far as I can tell, there is no
clean way to use a signed 8-bit integer in dbus. The dbus byte type
seems incompatible with negative values in high-level languages (python)
without awkward usage manipulation on the client side. For this reason,
I chose to use an int16_t type for the tx power dbus field, which is
then downcasted to the int8_t in bluetoothd, which at least makes the
signed-ness of the type crystal clear to the dbus client that uses it.

This change is manually verified by ensuring the intervals and tx power
parameters are correctly parsed from the LEAdvertisement1 object, and
that the parse fails if the parameters are incorrect or not compatible
with each other.

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>